Melt the butter in the microwave or in a small saucepan over low-medium heat.
Pour the melted butter into a big mixing bowl and let it cool down to room temperature in the fridge.
Once the butter has reached room temperature add the granulated sugar and whisk it together for 1 minute.
Add the egg, vanilla extract and mix it in until combined.
In a separate bowl, stir together flour, baking powder, baking soda, matcha powder, and salt.
Add the dry ingredients and mix it together until combined.
Using a cookie scoop, scoop out 11 cookies and place them on a tray lined with baking paper.
Roll them between your hands into a ball and give them a light press to flatten slightly.
Place the prepared cookies in the fridge to set for 30 minutes.
Preheat the oven at 180ºC / 355ºF and prepare a baking sheet with baking paper.
Place 6 cookies on a lined baking sheet and bake for 10-11 minutes.
Let them cool down on the baking tray for 3 minutes.
Use a spatula to lift them onto a cooling rack and let them cool down completely.
In a medium bowl, whip together all of the mascarpone cream ingredients until it reaches stiff peaks.
Pipe the mascarpone cream on top of the cookies in a swirl.
Finish the cookies with a dusting of matcha powder.